Field of the Invention
The present invention relates to an optical apparatus, such as a camera and an interchangeable lens, configured to perform processing for displaying object distance information.
Description of the Related Art
There is known an image pickup lens that can display object distance information calculated based on a position of a focus lens, on a display device such as a liquid crystal panel. There is also known a rear focus type image pickup lens that moves a lens for focusing which is disposed on an image side of the lens that is closest to the object side. The rear focus type image pickup lens can maintain an in-focus state by moving the focus lens so as to correct image plane fluctuations caused when the magnification varying lens is moved.
A distance display apparatus disclosed in Japanese Patent Laid-Open No. (“JP”) 7-306356 stores cam information indicative of the position of the focus lens and the position of the magnification varying lens for each object distance so as to maintain the in-focus state. The distance display apparatus displays object distance information on the display device based on the positions of the focus lens and the magnification varying lens and the cam information.
The distance display apparatus disclosed in JP 7-306356 stores cam information for each object distance, and calculates object distance based on the position of the magnification varying lens and the position of the focus lens.
In order to display the correct object distance in zooming in the rear focus type image pickup lens, it is necessary to drive the focus lens so as to make it follow the moving magnification varying lens. If the object distance is calculated while the focus lens is lagging behind in follow-up, an incorrect object distance is calculated. For example, when the magnification varying lens moves too fast, it is difficult to drive the focus lens so as to make it follow the magnification varying lens.
The follow-up lag of the focus lens does not always occur, and may be eliminated as time elapses. After the follow-up lag of the focus lens is eliminated, the object distance can be correctly calculated and thus the display content of the object distance changes before and after the follow-up lag is eliminated. This display content change of the object distance confuses the user.